More particularly, the invention pertains to an optical detection device for characterizing in terms of amplitude and phase the electromagnetic field of a zone of a sample, the device comprising a light source adapted to emit a light beam whose electromagnetic field has an angular frequency ω, a means adapted to divide the beam into a first beam defining a first pathway, termed the reference pathway, and a second beam defining a second pathway, termed the sample pathway, a modulation system which frequency-shifts the electromagnetic fields of the two beams by a frequency δ, a beam coupler adapted to collect the beams arising from the two pathways, an optical detection system adapted to detect the signal arising from the interference between the beams arising from the two pathways and coupled via said beam coupler.
The document “Numerical heterodyne holography with two-dimensional photodetector arrays” F. Le Clerc & co., Optics letters, describes an example of such an optical detection device using heterodyne detection to characterize in terms of amplitude and phase the electromagnetic field which passes through a sample, by a heterodyne numerical holography technique.
However, such a device requires the use of a matrix detector, thereby limiting the range of wavelengths in which the measurements can be carried out. The spatial resolution of such a device is moreover limited by the wavelength used.